The present invention relates to a carburetor arrangement for an internal combustion engine, especially for an internal combustion engine in a manually-guided implement such as a power chain saw, a brush cutter, a cut-off machine, or the like, which engine is to be started by a pull-cord.
Carburetor arrangements for two-cycle engines, for manually-guided implements, and that are to be started via a pull cord, are known in general. Opening into the intake channel portion is a fuel channel that is connected with a fuel-filled storage space and that supplies fuel as a function of the underpressure in the intake channel. Since internal combustion engines that are to be started by a pull cord achieve only low starting speeds, for the start-up via a start-up mechanism the intake underpressure is increased in that for example a choke valve reduces the flow cross-section of the intake channel portion upstream of the carburetor arrangement. This ensures that even with a pull cord starter, adequate fuel is drawn in during the start-up process, so that a mixture that is capable of being ignited is made available with few starting strokes, and ensures a start-up of the internal combustion engine.
The drawback of such start-up mechanisms that increase the intake underpressure is that they are also operational as the internal combustion engine starts up, so that the accelerating internal combustion engine leads to a sharp increase of the intake underpressure and hence to an increased supply of fuel, as a result of which the mixture becomes very rich. As a result, the mixture becomes overly rich as the internal combustion engine accelerates, and the engine dies. As the internal combustion engine starts up, the operator must therefore open the choke in a timely manner and at the same time must see to it that during the warm-up phase, the mixture does not become lean, by complete opening of the choke to such an extent that the engine dies.
It is therefore an object of the present invention to provide a carburetor arrangement such that with the choke engaged and the internal combustion engine accelerating, a dying of the engine due to an overly rich mixture is reliably prevented.